In late years, as a metal nanoparticle for junction use or metal pattern formation, there has been done the development of the composite nanometal particle that the organic coating layer comprising various kinds of organic substance surrounds the metal core of less than or equal to 100 nm. By way of example only, in example 1 of Japanese Patent Laid-Open No. 10-183207 (Patent Document 1), it is described the ultrafine particle having the organic coating layer of stearic acid surrounding the core of metal silver. In addition, in WO2009/090846 bulletin (Patent Document 2), the present inventors disclose the composite nanosilver particle in which the organic coating layer such as alcohol molecule or alcohol derivative is formed around the silver core. These nanoparticles are kneaded and mixed with a resin and a solvent to a paste, and this paste is employed for semiconductor junction and used to printing ink. Extent of particle size of a nanoparticle and its uniformity of particle size participate in a quality of paste greatly. Therefore, the development of an apparatus mass-producing the minute nanoparticles with good uniformity is extremely important.
As an approach to produce nanoparticles, there are the solid phase method, the liquid phase method and the gas phase method. Since nanoparticles are produced by melting a solid in the solid phase method, a large quantity of nanoparticles can be obtained because of a large amount of material, but there are many cases that the particle size becomes large, the cohesion is cruel and the uniformity of particle size is difficult. Since nanoparticles are produced by means of gaseous reaction in the gas phase method, an amount of substance becomes small, and it is not suitable for a large amount production of nanoparticles. Thus the liquid phase method has been developed. In the liquid phase method, an ingredient material is dispersed or dissolved in a solvent to form a solution, and nanoparticles are manufactured through solution reaction, so that a large amount production of nanoparticles become possible because of a large amount of substance. Besides, if the concentration is adjusted, it is advantageous in that the uniformity of particle size of nanoparticles is easy to be achieved.
As the liquid phase method to produce nanoparticles, Japanese Patent Laid-Open No. 2005-264199 bulletin (Patent Document 3), JP-T 2006-503790 bulletin (Patent Document 4) and Japanese Patent Laid-Open No. 2008-285749 bulletin (Patent Document 5) are known.
The nanoparticle production apparatus of Patent Document 3 is shown in FIG. 20 of the present patent application. In FIG. 20, 101 is the micro-reactor, 102 the ultrasonic generator, 103 the water bath, 104 the reaction unit, 105 the base plate, 106 the middle lamination thin plate, 107 the top plate, 108 the inflow line, 109 the microchannel, 110 the outflow outlet, 126 the engaging bolt, 126 the supersonic wave, 126a the part which is strengthened by supersonic wave interference, and 126b the part which is weakened by supersonic wave interference.
The function of this micro reactor 101 makes a metal salt aqueous solution flow into the inflow line 108, irradiates the supersonic wave into the microchannel 109 (109a, 109b) of size of several μm to several hundreds μm in diameter and generates the metal ultrafine particles (nanoparticles) in the aqueous solution from the metal salt using the supersonic wave energy.
The nanoparticle production apparatus of patent document 4 is shown in FIG. 21 of the present patent application. FIG. 21A) shows the nanoparticle production apparatus of straight tube type, where 201 is the reactor, 202 the reaction tube, 203a the zirconium salt solution (ingredient aqueous solution), 203b the suspension liquid, 204 the precipitation particle, 205 the reaction mixture (precipitation solution), 206 the hydrous zirconia sol, 207 the heating medium, 207a the inlet, 207b the outlet, 208 the velocity gradient formed in the interior of the reaction tube, 212 the pH moderator, and 213 the mixer.
As the function of this reactor 201, the heating medium 207 flows from the inlet 207a to the outlet 207b, and the precipitation particle 204 (hydrous zirconia nanoparticle) is generated when heating the ingredient aqueous solution 203a in the reaction tube 202, so that the hydrous zirconia sol 206 is emitted. However, as the generation condition of nanoparticles, it is described in the paragraph [0052] that the cross section diameter of the reaction tube is preferred at 0.01 cm-5 cm, it is described in the paragraph [0041] that the zirconium salt solution is preferred at the state without vortex, namely at the laminar flow state, and it is described in the paragraph [0049] that the flow velocity u of the zirconium salt solution is preferred at that the mean flow-time in the reaction tube is determined to be 1-60 seconds. However, there are weak points that the mass production of nanoparticles is difficult because the collision probability becomes small in the laminar flow state and the control of the production apparatus is difficult because nanoparticles are manufactured in an extremely short time of 1-60 seconds.
Furthermore, although FIG. (21B) shows the nanoparticle production apparatus of spiral tube type, the reaction tube 202 is only changed to the spiral tube type to lengthen the reaction time, and other conditions are similar with FIG. (21A). That is to say, it is wished that the solution flows with the laminar flow condition in the reaction tube, and it is unchanged that the residence time in the total length of the spiral tube is a short time of 1-60 seconds. Therefore, the mass production of nanoparticles is unsuitable and the difficulty of generation control exists as a weak point.
The nanoparticle production apparatus of patent document 5 is shown in FIG. 22 of the present patent application. In FIG. 22, 310 is the precursor feed portion, 320 the first heating portion, 321 the first circulatory device, 330 the second heating portion, 331 the second circulatory device, 340 the cooling portion and 350 the transfer apparatus. In addition, in the first heating portion 320 and the second heating portion 330, the reactor channel of capacitor type with the spiral form structure of 1.50 mm in diameter is built-in, and the coil tube of the reactor channel (spiral tube) becomes to be heated by heat value of the heating portion. According to this nanoparticle production apparatus, firstly the precursor solution of metal nanoparticle is supplied from the precursor feed portion 310 to the first heating portion 320 through the transfer apparatus 350, and the precursor solution is preheated by the temperature which does not cause the nanoparticle generation in the first heating portion 320 kept warm by the first circulatory device 321. Next, the preheated precursor solution is transferred to the second heating portion 330, and the nanoparticles are generated in the reaction channel inside of the second heating portion kept warm at the temperature which causes the nanoparticle generation by the second circulatory device 331. And the generated nanoparticle solution is transferred to the cooling portion 340 and is cooled off, so that the nanoparticle generation is stopped.